1. Field of the Invention
The invention pertains to the field of chains. More particularly, the invention pertains to a structure for restraining chordal oscillation of a chain.
2. Description of Related Art
A power transmission chain for use in an automobile or motorcycle is generally constructed from multiple links that are connected endlessly by connecting pins inserted into pin apertures of the links. In the operation of a power transmission chain, when the engagement frequency, determined by the number of teeth and the rotational speed of a sprocket around which a chain is wrapped, coincides with the resonance frequency of a chain, determined by the length of a chain span and chain tension, resonance occurs in the chain span and the span oscillates severely in a lateral direction.
Various efforts have been made in the prior art to prevent such resonant oscillation of a chain span. Leaf springs are commonly used to apply a biased force along the length of the connecting pin perpendicular to the direction of articulation of the chain. This spring force causes frictional resistance to any bending motion of the chain. While the leaf spring may successfully control resonant oscillations of the chain, it also increases frictional losses during articulation of the chain, thereby making it less efficient in transferring power between sprockets.
Japanese patent application laid-open publication No. 55-34580 (JP55-34580) discloses two adjacent connecting pins of two adjacent links that are coupled to each other via a leaf spring in order to decrease the engagement collision sound of a roller chain. JP55-34580 describes that the links articulate against the spring force of a leaf spring at the time of articulating motion of the adjacent links, thereby restraining rapid articulation of the links during the engagement with the sprocket teeth to decrease the engagement collision sound. Also, in this case, chordal oscillation of a chain span may be restrained due to the restriction of articulating motion of the links.
However, in this prior art structure, since opposite end portions of the leaf spring need to be fixedly attached to the end portions of the connecting pins, the end portions of the connecting pins require caulking, thereby making the assembly work troublesome. Moreover, the width of a chain is increased by the width of the leaf spring. Also, JP55-34580 discloses the use of a torsional coil spring to decrease the width of a chain. However, in this case, each connecting pin requires a torsional coil spring, thereby making the structure and the assembly work complicated and troublesome.
The present invention simplifies the structure for restraining chordal oscillation of a chain span of a power transmission chain while minimizing frictional losses and simplifying the assembly work of the chain.